1. Field of the Invention
The present invention relates to a circuit substrate and more specifically relates to a circuit substrate preferably for use in a branch circuit including a high pass filter and a low pass filter. In addition, the present invention relates to a branch circuit including the circuit substrate.
2. Description of the Related Art
As an example of an invention relating to a circuit substrate of the related art, the splitter described in Japanese Unexamined Patent Application Publication No. 2005-323064 is known. FIG. 19 illustrates a splitter 100 described in Japanese Unexamined Patent Application Publication No. 2005-323064.
The splitter 100 includes first to third ports P1 to P3 and a high pass filter hpf and a low pass filter lpf. The first port P1 is an input port, and the second port P2 and the third port P3 are output ports. A signal path connected to the first port P1 branches and is connected to the second port P2 and the third port P3. In addition, the high pass filter hpf is provided between the first port P1 and the second port P2, and the low pass filter lpf is provided between the first port P1 and the third port P3.
In the splitter 100 described in Japanese Unexamined Patent Application Publication No. 2005-323064, the high pass filter hpf and the low pass filter lpf preferably include conductor layers provided in a circuit substrate of the splitter 100 and chip components provided on a surface of the circuit substrate. The port P1 and the high pass filter hpf are connected to each other by a signal line composed of a conductor layer provided in the circuit substrate. Since an unwanted inductor component is generated in such a signal line, impedance matching between the first port P1 and the second port P2 is disrupted. As a result, reflection of a signal occurs between the first port P1 and the second port P2 and loss occurs in the splitter 100.